1. Field of the Invention
The present invention relates to a used-master security system for a printing apparatus that can prohibit the removal of a used master and protect the master, a used-master security method for a printing apparatus in which the used-master security system for a printing apparatus is used, and a printing apparatus in which the used-master security system for a printing apparatus can prohibit the removal of a used master.
2. Description of the Related Art
A printing apparatus is conventionally used for printing several sheets and for other purposes. Known types of printing apparatuses that wind a so-called master on a plate cylinder to carry out printing include examples cited in Japanese Patent Application Laid-open Nos. S59-198185 (Prior Art 1), S63-74679 (Prior Art 2), H8-183238 (Prior Art 3), H9-71029 (Prior Art 4), and 2002-86882 (Prior Art 5). This type of printing apparatus has a drawback in that the information recorded on the master may be revealed. In other words, if the master is left wound on the plate cylinder when printing is completed, another person may thereafter print using this master, so it is possible that the information recorded on the master may be revealed. There is, therefore, a drawback from the aspect of managing sensitive information, particularly in public agencies, schools, businesses, and other environments in which many people use such a printing apparatus.
In view of the above, printing apparatuses that prevent other people from printing using the master after printing is completed have been proposed in the disclosures of prior arts 1 to 4 noted above. However, the arts disclosed in these instances of prior art, while preventing other people from performing printing by using the master after printing is completed, and preventing revelation of the information recorded on the master by further printing, still allow the master after printing is completed to be stored inside the printing apparatus, so there is still a drawback from the aspect of managing sensitive information in that the used master can be freely removed from the printing apparatus.
In view of the above, the prior art 5 noted above proposes an art that applies heat and shrinks the master so that the information recorded on the used master cannot be read. According to this art, there is no drawback from the aspect of managing sensitive information even if the master after being shrunk through the application of heat can be freely removed from the printing apparatus. In the art disclosed in prior art 5, however, shrinking does not occur if the master is not composed of a heat shrinkable material, so there is a drawback in that the types of master that can be used are limited. There are also various types of heat shrinkable materials, there is disparity in the temperature that causes shrinkage, the heat shrinkable material itself and materials resulting from laminating other materials to the heat shrinkable material have a thermal capacity, and the thermal capacity differs according to the material, so when the heating temperature is set high so as to reliably shrink the master, there is a danger that the master will be excessively heated when using a material with a low heat-shrinking temperature or when using a material with a small thermal capacity.
Technologies relating to the present invention are (also) disclosed in, e.g., Japanese Patent Application Laid-open No. H10-226147.